The present invention relates to the field of tank agitators. The type of agitation used in a tank determines the type of result achieved. To vary the agitation it is desirable, in addition to varying the drive power and ratio driving the blade shafts, to vary the pitch of the agitator blades. The pitch affects the speed and power absorption, and interacts with motor power and drive ratio.
Whether it is used in the preparation of food, a chemical or other processess the orientation of the agitator blades directly impacts upon the type of product and quality of product produced within the tank. Therefore, it is desirable that the position of the agitator used be variable so that the product can be produced with maximum efficiency.
Traditionally, changing the position or pitch of an agitator blade has been a time consuming process. There have been many attempts to make this simpler. For example, (Mahler), U.S. Pat. No. 4,456,382 shows an agitator hub that is designed to be used in an agitation tank just as the present invention is to used. However, the Mahler patent is structurally very different from the instant invention. The Mahler patent discloses a round shaft to which a hub in two pieces is affixed. The hub and central shaft are held to each other by use of a locking bolt. The two pieces of the hub are designed to slide vertically up and down the shaft. There is a recess or opening that is formed by the combination of the two pieces of the hub. Into this opening the shaft of the paddle that is used is placed. The shaft of the paddle is held in whatever desired position by the pressure of the two pieces of the hub which are clamped around the paddle shaft. The connection of the central shaft and the hub could slip. For example the central shaft could rotate, despite the locking bolt, with respect to the hub. The paddle could rotate or slip with respect to the hub. The present invention is designed in such a manner that is impossible for the hub to slip with respect to the shaft and it is impossible for the shaft of the paddle to slip with respect to the hub. Furthermore, the hub is not two separate pieces but one piece. Also, the Mahler patent does not disclose the use of seals to aid in keeping the machine clean and sanitary.
Another patent, (Altofer), U.S. Pat. No. 1,745,595 shows a radically different type of stirrer than that which is contemplated in the invention. The stirrer shown is somewhat adjustable in position because of the fact that the shaft 2 at the bottom of FIG. 1 (as disclosed in the patent) is square in cross section. The same is true of the shaft 13. However, this is not a practical adjustment and is not the type of adjustment contemplated by the applicant's invention. (Parsons), U.S. Pat. No. 1,812,831 shows adjustment of the blade of an aircraft propeller. Again, both the mechanical construction and the purpose are different from the applicant's invention. (Forest), U.S. Pat. No. 2,636,721 is somewhat closer to the applicant's invention but the impellers of the Forest patent are mounted on hubs that are shaped like pinion gears and are captured inside of a bolt-together housing. By unbolting the housing the angle of the impeller can be changed. Again this is not similar in mechanical construction or purpose to the applicant's invention. Also, it would appear that sealing and cleaning the Forest patent would be a serious problem if it was used in a structure that required cleaning; for instance, a food or chemical agitator tank. The same can be said of (Hall) U.S. Pat. No. 2,641,984. The Hall patent is not intended to stir food products or chemicals, only earth. (Mohn), U.S. Pat. No. 3,077,228 is cited because it uses set screws to effect an adjustment but the purpose, structure and function of the Mohn patent is different from that of the applicant's invention. (Lutz), U.S. Pat. No. 4,304,494 does show an adjustable paddle but the concept and structure are completely different from the applicant's invention as Lutz discloses a slip-on shroud to protect the shank of a mixing paddle of an asphalt mixer. A simple examination of the drawings of the Lutz patent, as well as the claims, show how radically different it is from the present invention. (H. Malm), U.S. Pat. No. 1,634,330 discloses a marine propeller with means for adjusting the pitch of the blades. However, the shaft to which the hub of the Malm invention is attached must be round and no method for sealing the connections between the blades, the hub, and the shaft is disclosed. Therefore, cleaning and maintaining the Malm propeller in connection with processing of food would be much harder than with the applicant's invention. Also the structure of the Malm invention is different from the applicant's invention. (W. L. Effinger, Jr.), U.S. Pat. No. 3,272,714 discloses an adjustable propeller that is adapted for use in model airplanes. The blades are held in the hub by frictional means. The invention is structurally different from the applicant's invention and does not have the same proposed use. (A. E. Dehnicke), U.S. Pat. No. 2,563,011 discloses a two-part hub adjustable pitch fan for use in an automobile engine. The adjustment of one blade of this fan will adjust all the other blades of this fan. Furthermore, the structure of the Dehnicke invention is different from that of the applicant's invention. Also, since the adjustment of one blade would adjust all blades in the Dehnicke invention it would not meet the requirements of the applicant's invention since it may be necessary to have the blades in the applicant's invention be of differing pitches or two of the same pitch and one of a different pitch, etc. This would not be possible with the Dehnicke invention. (Wennberg et al), U.S. Pat. No. 4,150,921 discloses marine propellers that are constructed with a split-hub design. The propellers are screwed into the hub which is completely different in concept and structure from the applicant's invention. Also, the purpose of the Wennberg patent is not the purpose of the applicant's invention.
None of the above prior art known to the inventor teach a structure that wouold suggest applicant's invention. The closest reference is believed to be the Mahler patent and the applicant's invention is significantly different from that patent in structure. The inventor knows of no other prior art that is closer to his invention than the Mahler patent.
Other advantages and features, as well as objects, of the invention will become apparent from the ensuing description of a preferred embodiment, taken with reference to the appended drawings.